Antenna system



L. c. VAN ATTA. ET AL 2,908,904

ANTENNA SYSTEM Filed Aug. 26, 1955 United "States Patent ANTENNA SYSTEMLester C. Van Atta and Mack D. Adcock, Pacific Palisades, andThomas-Kinaga, Los Angeles, Calif., as- I signers to Hughes AircraftCompany, Culver City, Calif., a corporation of Delaware ApplicationAugust 26, 1955, Serial No. 530,826

3 Claims. (Cl. 343708) This invention relates to antenna systems, andparticularly to radiating antenna arrays which may be used in high speedaircraft.

'. Modern aircraft are increasingly using electronic equipment for.communication and navigation. It is usually essential that there be aslittle' interference as possible with the normal operation of theaircraft. Specifically, the electronic equipment should be as light inweight as practicable, and introduce as little air resistance aspossible.

Structures which employ a portion of the aircraft itself asan antennastructure are known. For example, a portion of a vertical tail surfacemay be employed as a radiating surface for the aircraft. Such antennasare usullyelectiically isolated from the remainder of the aircraft by asection of dielectric material. When it has been desired to provide anadditional antenna array, the mechanical and electrical arrangementshave not been entirely satisfactory. The supplemental antenna arraysheretofore used have been heavy or have adversely affected thestreamlining of the aircraft, or both. Further, the types of couplingemployed to cross the dielectric isolating section have introducedexcessive capacitance into the structure, caused excessive signal loss,or increased dangers due to voltage breakdown and lightning discharge:It has been particularly diflicult to provide a supplemental antennaarray which has an omnidirectional horizontal pattern, and which at thesame time has the desired mechanical properties and which can be fedwithout the insertion of undesired electrical properties into thesystem.

.It is therefore an object of this invention to provide an improvedaircraft antenna structure having less effect on, aircraft performanceand better electrical characteristics than the antennas of the priorart.

It is another object of this invention to provide a compact andlightweight supplemental antenna arrangement for use with an antennacomprised of a portion of an aircraft body.

- It is a further object of this invention to provide an improvedsupplemental antenna arrangement for an aircraft antenna utilizing anisolated portion of a control surface, the supplemental antennaproviding negligible wind resistance and being relatively free fromlightning discharge effects, excessive capacitance, and the possibilityof voltage breakdown.

; It is still another object of this invention to provide an improvedantenna arrangement for aircraft, which arrangement presents a minimumof air resistance and an omnidirectional pattern in the horizontalplane.

' 'It is another object of this invention to provide an improvedsupplemental antenna arrangement for the vertical control surface of anaircraft.

' An antenna structure in accordance with this invention may utilize asone radiating body a portion of an electrically isolated aircraftvertical control surface. A

supplemental antenna comprising a rectangular wave guide section may bemounted on a topmost portion of 2,908,904 Patented Oct. 13, 1959 ice thevertical control surface. The rectangular waveguide section may haveradiating slots in each side parallel to the direction of movement ofthe aircraft, to provide an omnidirectional pattern in the horizontal.plane and a narrow pattern in the vertical plane. Streamlining sectionsfore and aft of the supplemental antenna may mini mize the airresistance presented by the antenna without affecting the radiationpattern afforded. Signals may be provided to the supplemental antennathrough a dielectric coupling member comprising a dielectric waveguidewithin a dielectric cover. The dielectric coupling member is arranged tospan the elements which electrically isolate the vertical controlsurface radiating body from the remainder of the aircraft. Thedielectric coupling member feeds the supplemental antenna withoutintroducing undesired electrical characteristics into the verticalcontrol surface antenna arrangement.

The novel features of this invention, as well as the invention itself,both as to its organization and method of operation, may best beunderstood when considered in the light of the following description,when taken in connection with the accompanying drawing, in which likereference numerals refer to like parts, and in which:

Fig. 1 is a perspective view, partly broken away, of'a portion of anaircraft employing an antenna arrangement, including a supplementalantenna and a dielectric coupling member, in accordance with thisinvention;

Fig. 2 is a detailed perspective broken away section of a dielectriccoupling member which may be employed in the arrangement of Fig. 1, and

Fig. 3 is a detailed perspective view of a supplemental antenna whichmay be employed in the arrangement of Fig. 1.

An antenna array in accordance with the invention, referring now toFigs. 1, 2, and 3, may be mounted on and include a portion of anaircraft body 10. The antenna arrangement may include a portion of avertical I from the remainder of the aircraft 10 by a band ofelecelectrical portions.

trically isolating material, such as a dielectric material. Theisolating body 16 thus'defines an electrical gap between the tail capportion 14 and the body of the aircraft 10, and divides the verticalcontrol surface 12 into two The tail cap portion 14 may thereforecomprise a planar wave energy radiating structure, and may be fed byenergizing means (not shown) mounted in the body of the aircraft 10. Thetail cap 14 may be at least partially hollow, or provided with aninternal aperture for coupling associated elements.

A supplemental antenna 20 chiefly comprising a rectangular waveguide 22having radiating slots 24 on the opposite faces thereof, may be mountedon an uppermost point of the tail cap portion 14. The broad faces of therectangular waveguide 22 are parallel to the normal direction ofmovement of the aircraft 10, and the radiating slots 24 are provided ineach of these broad faces. In accordance with techniques well known inthe antenna art, the radiating slots may be so positioned as to providean omnidirectional pattern in the horizontal plane, and a relativelynarrow pattern in the vertical plane. A pair of streamlining sections 26may be mounted fore and aft, respectively, of the rectangular waveguide22, to provide a smooth fairing for the rectangular waveguide antenna 22in the normal direction of movement of the aircraft 10. A dielectriccoupling member 30, best seen in Fig. 2, may be employed to bridge thedielectric isolating body 16 shown in Fig. l. The dielectric couplingmember 30 may include a central cylindrical dielectric waveguide 32having slightly expanded end portions 34 and pointed tips 36. A covercomprising a hollow cylindrical dieach end encompasses the centralcylindrical dielectric waveguide 32. Each of the end portions 34 of thedielectric waveguide 32 registers with a different one of the horns 40coupled to the cylindrical shell 38, and forms therewith a transitionsection. Elongated tips of the horn sections 40 may be coupled toconductive waveguide sections 42, 44 including circular to rectangulartransition sections. A first of the conductive waveguides 42 couples thedielectric coupling member 30 to the supplemental antenna 29 through thehollow central section of the tail cap 14. The second of the conductivewaveguides 44 couples the dielectric coupling member 30 to theassociated electrical epuipment in the aircraft 10. The shell 38 may bepressurized, if desired.

In operation, still referring to the figures of the drawing, the tailcap antenna 14 is energized by a source within the aircraft 10, andthereby provides a radiation pat tern at a frequency band determined bythe physical configuration of that portion of the vertical controlsurface 12. The supplemental antenna 20 mounted on top of the tail capantenna 14 provides a separate radiation pattern from the patternprovided by the tail cap antenna 14. Note that the rectangular waveguideantenna 22 employed is small with respect to the vertical controlsurface 12 and that the radiating slots 24 are exposed, to provide thedesired omnidirectional horizontal pattern without interference. Thestreamlining sections 26 reduce the air resistance of the supplementalantenna 22 to a negligible amount, without affecting the radiationpattern of the supplemental antenna 22. Thus the arrangement providedavoids difficulties heretofore encountered through the use ofcylindrical waveguides and cumbersome, energy absorbing, radomes.

Electrical isolation of the tail cap antenna 14 from all but the energysupplied directly to it is maintained by the use of the primarilydielectric coupling member 30. Energy provided from the equipment in theaircraft through the conductive waveguide 44 is impressed on one end ofthe dielectric coupling member 30 at a horn 40. The energy at the hornis transferred to the end 34 of the central cylindrical dielectricwaveguide 32, passes along the waveguide 32 to the opposing end, and istransferred through the other horn 40 to the conductive waveguide 42 atthe opposing end. The conductive-waveguide 42 impresses the energy onthe supplemental antenna 22. The pointed tips 36 on the dielectricwaveguide 32 form, with the elongated tips on the horns 40 coupled tothe dielectric shell 38, a smooth transition section, without reflectioneffects, for the transfer of energy.

The presence of this type of dielectric coupling member 30 within thedielectric isolating body 16 maintains the tail cap antenna 14electrically separate from the remainder of the aircraft 10. Thus thetail cap antenna 14 is protected against voltage breakdown, and nocapacitance is introduced beyond the inherent capacitance of the system.Further, dangers due to lightning discharge are also minimized. Notethat the cylindrical shell 38 in the dielectric coupling member 30permits the coupling member 30 to be pressurized, and at the same timeprovides structural strength and rigidity for the system. The couplingarrangement thus provided may be employed in the microwave frequencyrange, obviating the need for complicated coupling arrangementsheretofore used with other frequencies. The tail cap antenna arrangementwill, by its nature, operate in a frequency band materially differentfrom that of the microwave frenquency.

Thus there has been provided an improved antenna structure foremployment in aircraft. An omnidirectional horizontal pattern may beprovided without disturbing the performance of an antenna integral withthe airplane, and without introducing undesired electrical effects oradversely affecting the performance of the integral antenna.

What is claimed is:

1. An antenna structure for employment with an aircraft having avertical control surface and comprising: a band of dielectric materialmounted between the ends of said vertical control surface and separatingsaid surface into two portions, the furthest portion of the verticalcontrol surface from the aircraft body providing a wave energy radiatingsurface arranged to radiate energy in a first predetermined frequencyband; a rectangular waveguide member mounted in the uppermost portion ofsaid furthest portion, said rectangular waveguide including radiatingapertures on each side thereof parallel to the longitudinal axis of saidvertical control surface and being arranged to radiate energy in asecond predetermined frequency band; a pair of streamlining surfaces,mounted fore and aft, respectively, of said rectangular waveguide on theradiating portion of the vertical control surface and defining with saidrectangular waveguide a streamlined projection; waveguide means withinthe radiating portion of the vertical control surface and coupled tosaid waveguide antenna for supplying energy thereto; and a couplingmember mounted within said band of dielectric material, said couplingmember including a central cylindrical shell of dielectric material, apair of horn members, one mounted on each end of said central shellcoaxial therewith and pointing away from said shell, and a tubulardielectric waveguide mounted within and coaxial with said shell, andincluding a pointed tip portion at each end thereof, each of said tipportions being in registry with the narrow portion of a different one ofthe horn members coupled to said cylindrical shell, one of said hornmembers being an input member and adapted to be responsive to energy tobe applied to said rectangular waveguide member, the other of said hornmembers being an output member and coupled to the waveguide means forsupplying energy to said rectangular waveguide antenna.

2. A dual antenna structure for an aircraft having a vertical controlsurface and comprising: a dielectric isolating section isolating theupper portion of said vertical control surface electrically from theremainder of the aircraft, said upper portion thereby providing aradiating surface for radiating energy in a first predeterminedfrequency band; a rectangular waveguide antenna, mounted in the topportion of said vertical control surface upperportion, and includingradiating slots in each side thereof parallel to the usual direction offlight of the aircraft for radiating energy in a second predeterminedfrequency band, the pattern of radiation provided by said rectangularwaveguide antenna being substantially omnidirectional in the horizontalplane and relatively narrow in the vertical plane; streamlining sectionsmounted in said vertical control surface upper portion adjacent saidrectangular waveguide antenna, said two streamlining sections being foreand aft, respectively, of said rectangular waveguide antenna withrespect to the usual direction of movement of said aircraft; adielectric coupling member mounted within the dielectric isolatingsection in the vertical control surface and including a centralcylindrical dielectric waveguide having pointed end portions, adielectric cover member encompassing said central cylindrical waveguideand coaxial therewith, and a pair of terminating metal transitionmembers, each encircling the point at a different end of said centralcylindrical dielectric waveguide and forming with the associated point atransition section for the transfer of energy; and conductive waveguidemeans within said vertical control surface upper portion and couplingsaid dielectric coupling member to said rectangular waveguide antenna.

3. A dual antenna structure comprising: a conductive structure having asubstantially planar surface; a dielectric isolating section within saidconductive structure at an intermediate point and isolating a terminalportion of said conductive structure electrically from the remainderfirst antenna and coupling said dielectric waveguide to said secondantenna.

References Cited in the file of this patent UNITED STATES PATENTSSouthworth Aug. 6, 1946 Babcock et a1. May 19, 1953 cal Feb. 1, 1955Kandoian et a1. Dec. 6, 1955

